1. Field of the Invention
The present invention relates to a novel ink jet recording ink, used in a method for ink jet recording, and an ink jet recording method.
2. Description of the Related Art
So-called ink jet printers capable of recording images on paper, cloth, or a film by discharging a liquid or molten solid ink through nozzles, slits, a porous film, and the like have advantages of small size, low cost, low noise, and the like, and have been widely put on the market as black monochrome or color printers. Among them, a so-called piezoelectric ink jet method using a piezoelectric element or a so-called thermal ink jet method, which conducts recording by applying thermal energy to form liquid drops, has many advantages such as high-speed printing, high resolution, and the like.
Many characteristics are required of ink jet recording ink. Among them, the following characteristics are important:
(1) Excellent images free of omissions and unevenness are obtained irrespective of printing speed and printing pattern. PA0 (2) In the thermal ink jet method, there is no kogation due to temperature change on a heater which forms and develops bubbles at high temperatures, and there is no short-circuiting of acting electrodes in the heater portion that would prevent the heater from operating (fail) by eroding a material usually in contact with an ink. PA0 (3) The ink can be stored for a long period of time. PA0 (4) The formed images have excellent storage stability. PA0 (5) The formed images have excellent fixing properties.
There have conventionally been many suggestions that have been carried out to provide the above-mentioned characteristics.
Among conventional ink jet recording inks, an ink using an aqueous dye as a coloring material is mainly used. However, it has problems in water resistance and lightfastness, and the storage stability of images is not necessarily satisfactory. On the other hand, an ink using a pigment as a colorant can improve water fastness and lightfastness, and can provide an image having high optical density and no blotting. Therefore, this ink is very promising and there have recently been many suggestions concerning the ink which have been put into practice. For example, Japanese Patent Application Laid-Open (JP-A) No. 56(1981)-147871 suggests a recording liquid comprising an aqueous medium containing at least a pigment, a high-molecular dispersant, and a nonionic surfactant. Further, U.S. Pat. Nos. 5,085,698 and 5,221,334 suggest the use of a block copolymer comprising hydrophilic polymer portion-hydrophobic polymer portion or hydrophobic polymer portion-hydrophilic polymer portion-hydrophobic polymer portion as a dispersant for a pigment. Further, U.S. Pat. No. 5,172,133 suggests the use of a specific pigment, water-soluble resin, and solvent. However, in the conventionally suggested inks, stability for a long period of time, including environmental changes, may not be easily attained. Further, when a metal or metal oxide exists on an ink flow route in a cartridge-constituting material or print-head-constituting material, a pigment is deposited on them, and consequently, stable ejection is liable to be disturbed (namely, clogging) and excellent fixation cannot be provided on various papers. Particularly, in the ink jet recording method, there is a disadvantage that the pigment deposited on a heater comprising a metal such as tantalum causes kogation due to temperature rising in printing and remarkably shortens the life of the print head.